System and method for dynamically improving call connection

ABSTRACT

A method for controlling an output of a power amplifier of a portable communication device includes determining a power level of a signal received at the portable communication device, generating a receive reference signal (RXLEV) that is indicative of the power level of the signal received at the portable communication device, and determining whether the receive reference signal is within a threshold value window. When the receive reference signal is within the threshold value window a nominal power output of a power amplifier in the portable communication device is transmitted during a random access channel signal transmission. When the receive reference signal is below the threshold value, a power output of the power amplifier in the portable communication device is increased during the random access channel signal transmission. When the receive reference signal is above the threshold value, a power output of the power amplifier in the portable communication device is decreased during the random access channel signal transmission.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/041,944, filed on Mar. 4, 2008, entitled “SYSTEM AND METHOD FORDYNAMICALLY IMPROVING CALL CONNECTION,” which is a non-provisionalapplication of U.S. Provisional Application No. 60/895,777, filed onMar. 20, 2007, entitled “IMPROVING CALL CONNECTION DYNAMICALLY,” thebenefits of the filing dates of which are hereby claimed and thespecifications of which are incorporated herein by this reference.

BACKGROUND

In a cellular-type communication system, a base station (BS)communicates with one or more mobile stations (MS) also referred to as ahandset. To register with the base station or to establish a call with abase station in the Global System for Mobile Communication (GSM) system,the mobile station must initiate the process by sending a random accessburst on what is referred to as random access channel (RACH). The randomaccess burst is referred to as a “RACH” or a “RACH burst.” Whenaccessing the base station using a RACH, the mobile station operating inthe GSM system must use the maximum transmit power that it is allowedwhen accessing the system. The GSM system includes a number of differentcommunication bands which are deployed throughout the world including,for example, the GSM 850 band deployed in the Americas, the GSM 900 banddeployed in Europe, the DCS 1800 band deployed in Europe and the PCS1900 band deployed in the Americas.

For example, in a class 4 mobile station operating in the GSM 900 band,output power is divided into a number of levels with output power level5 being the maximum power and corresponding to a 33 dBm, +/−2 dBnominally. This arrangement also applied to extended data rates for GSMevolution (EDGE), DCS and PCS systems.

In a GSM system, typically the maximum power the base station cantransmit is approximately 43 dBm and the maximum power that a class 4mobile station can transmit is 33 dBm, +/−2 dB. Other class mobilestations may have different maximum output power. The 10 dB differencein the downlink (base station to mobile station) versus the uplink(mobile station to base station) results in a transmission environmentin which the mobile station is said to be “uplink limited,” alsoreferred to as a situation in which the mobile station is said to be“disadvantaged” with respect to the base station. Further, a mobilestation can be uplink limited if it is distant from the base station orif the signal between the mobile station and the base station is highlyattenuated by the propagation media. When the mobile station is in sucha disadvantaged position, the 10 dB power difference may cause themobile station to experience degradation in its call connection metric.A call connection metric is an important metric typically used by anequipment manufacturers and network operators to differentiate theirbrand against others.

Therefore, it would be desirable to have a way to minimize the influenceof the uplink limited condition on the mobile station, and improve thecall connection metric.

SUMMARY

Embodiments of the invention include a method for controlling an outputof a power amplifier of a portable communication device, includingdetermining a power level of a signal received at the portablecommunication device, generating a receive reference signal (RXLEV) thatis indicative of the power level of the signal received at the portablecommunication device, and determining whether the receive referencesignal is within a threshold value window. When the receive referencesignal is within the threshold value window a nominal power output of apower amplifier in the portable communication device is transmittedduring a random access channel signal transmission. When the receivereference signal is below the threshold value, a power output of thepower amplifier in the portable communication device is increased duringthe random access channel signal transmission. When the receivereference signal is above the threshold value, a power output of thepower amplifier in the portable communication device is decreased duringthe random access channel signal transmission.

Related systems are also provided. Other systems, methods, features, andadvantages of the invention will be or become apparent to one with skillin the art upon examination of the following figures and detaileddescription. It is intended that all such additional systems, methods,features, and advantages be included within this description, be withinthe scope of the invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

The invention can be better understood with reference to the followingfigures. The components within the figures are not necessarily to scale,emphasis instead being placed upon clearly illustrating the principlesof the invention. Moreover, in the figures, like reference numeralsdesignate corresponding parts throughout the different views.

FIG. 1 is a block diagram illustrating a simplified portable transceiverincluding a power amplifier control element according to one embodimentof the system and method for dynamically improving call connection.

FIG. 2 is a schematic diagram illustrating a communication environmentin which the system and method for dynamically improving call connectionoperates.

FIG. 3 is a graphical representation of an output burst including adescription of the operation of the system and method for dynamicallyimproving call connection.

FIG. 4 is a graphical representation of a portion of the output burst ofFIG. 3, illustrating the operation of the system and method fordynamically improving call connection.

FIG. 5 is a flow chart illustrating the operation of an embodiment of amethod for dynamically improving call connection.

FIG. 6 is a flow chart illustrating the operation of an alternativeembodiment of a method for dynamically improving call connection.

FIG. 7 is a flow chart illustrating the operation of another alternativeembodiment of the method for dynamically improving call connection.

DETAILED DESCRIPTION

Although described with particular reference to a portable transceiveroperating in the Global System for Mobile Communication (GSM) system,the system and method for dynamically improving call connection can beimplemented in any communication device that accesses a random channelusing maximum power to initiate a connection.

The system and method for dynamically improving call connection can beimplemented in hardware, software, or a combination of hardware andsoftware. When implemented in hardware, the system and method fordynamically improving call connection can be implemented usingspecialized hardware elements and logic. When the system and method fordynamically improving call connection is implemented partially insoftware, the software portion can be used to control components in thepower amplifier control element so that various operating aspects can besoftware-controlled. The software can be stored in a memory and executedby a suitable instruction execution system (microprocessor). Thehardware implementation of the system and method for dynamicallyimproving call connection can include any or a combination of thefollowing technologies, which are all well known in the art: discreteelectronic components, a discrete logic circuit(s) having logic gatesfor implementing logic functions upon data signals, an applicationspecific integrated circuit having appropriate logic gates, aprogrammable gate array(s) (PGA), a field programmable gate array(FPGA), etc.

The software for the system and method for dynamically improving callconnection comprises an ordered listing of executable instructions forimplementing logical functions, and can be embodied in anycomputer-readable medium for use by or in connection with an instructionexecution system, apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions.

In the context of this document, a “computer-readable medium” can be anymeans that can contain, store, communicate, propagate, or transport theprogram for use by or in connection with the instruction executionsystem, apparatus, or device. The computer readable medium can be, forexample but not limited to, an electronic, magnetic, optical,electromagnetic, infrared, or semiconductor system, apparatus, device,or propagation medium. More specific examples (a non-exhaustive list) ofthe computer-readable medium would include the following: an electricalconnection (electronic) having one or more wires, a portable computerdiskette (magnetic), a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flash memory)(magnetic), an optical fiber (optical), and a portable compact discread-only memory (CDROM) (optical). Note that the computer-readablemedium could even be paper or another suitable medium upon which theprogram is printed, as the program can be electronically captured, viafor instance optical scanning of the paper or other medium, thencompiled, interpreted or otherwise processed in a suitable manner ifnecessary, and then stored in a computer memory.

FIG. 1 is a block diagram illustrating a simplified portable transceiver100 including an embodiment of a system and method for dynamicallyimproving call connection. The portable transceiver 100 includes aninput/output (I/O) element 102 coupled to a baseband subsystem 110 viaconnection 104. The I/O element 102 represents any interface with whicha user may interact with the portable communication device 100. Forexample, the I/O element 102 may include a speaker, a display, akeyboard, a microphone, a trackball, a thumbwheel, or any otheruser-interface element. A power source 142, which may be a directcurrent (DC) battery or other power source, is also connected to thebaseband subsystem 110 via connection 144 to provide power to theportable transceiver 100. In a particular embodiment, portabletransceiver 100 can be, for example but not limited to, a portabletelecommunication device such as a mobile cellular-type telephone.

The baseband subsystem 110 includes microprocessor (μP) 120, memory 122,analog circuitry 124, and digital signal processor (DSP) 126 incommunication via bus 128. Bus 128, although shown as a single bus, maybe implemented using multiple busses connected as necessary among thesubsystems within baseband subsystem 110.

Depending on the manner in which the system and method for dynamicallyimproving call connection is implemented, the baseband subsystem 110 mayalso include one or more of an application specific integrated circuit(ASIC), a field programmable gate array (FPGA), or any otherimplementation-specific or general processor.

Microprocessor 120 and memory 122 provide the signal timing, processingand storage functions for portable transceiver 100. Analog circuitry 124provides the analog processing functions for the signals within basebandsubsystem 110. The baseband subsystem 110 provides control signals aradio frequency (RF), mixed signal device (MSD) subsystem. 130. TheRF/MSD subsystem 130 may include a transmitter 150, a receiver 170,power amplifier 180, and a power amplifier control element 185. Theelements within the RF/MSD subsystem 130 can be controlled by signalsfrom the baseband subsystem 110 via connection 132. Alternatively, thetransmitter 150 and the receiver 170 may be located on an RF integratedcircuit (IC).

The baseband subsystem 110 generates various control signals, such as apower control signal, that is used to control the power amplifiercontrol element 185 and the power amplifier 180, as known to thoseskilled in the art. The control signals on connection 132 may originatefrom the DSP 126, the microprocessor 120, or from any other processorwithin the baseband subsystem 110, and are supplied to a variety ofconnections within the transmitter 150, receiver 170, power amplifier180, and the power amplifier control element 185. It should be notedthat, for simplicity, only the basic components of the portabletransceiver 100 are illustrated herein. The control signals provided bythe baseband subsystem 110 control the various components within theportable transceiver 100. Further, the function of the transmitter 150and the receiver 170 may be integrated into a transceiver.

The power amplifier control element 185 generates a power amplifier (PA)power control signal. The power control signal controls the power outputof the power amplifier 180 based on various inputs. For example, in anembodiment, a closed power control loop may influence the power outputof the power amplifier 180. In another embodiment, an open power controlloop may influence the power output of the power amplifier 180. Forexample, in an embodiment, a signal received by a base station withwhich the portable communication device 100 is communicating may issue apower control signal. In other embodiments, the baseband subsystem 110may provide a power profile signal to the power amplifier controlelement 185.

If portions of the system and method for dynamically improving callconnection are implemented in software that is executed by themicroprocessor 120, the memory 122 will also include power control level(PCL) software 155 a first register 156 and a second register 157. Thefirst register 157 can be configured to contain a threshold value forthe level of the received signal, RXLEV_THRESHOLD, and the register 157can be configured to contain a value of a power boost offset, referredto as PWR_BOOST_OFFSET, and a value for power decrease offset,PWR_DECREASE OFFSET, as will be described below. The power control level(PCL) software 155 comprises one or more executable code segments thatcan be stored in the memory and executed in the microprocessor 120.Alternatively, the functionality of the power control level (PCL)software 155 can be coded into an ASIC (not shown) or can be executed byan FPGA (not shown), or another device. Because the memory 122 can berewritable and because an FPGA is reprogrammable, updates to the powercontrol level (PCL) software 155 can be remotely sent to and saved inthe portable transceiver 100 when implemented using either of thesemethodologies.

Baseband subsystem 110 also includes analog-to-digital converter (ADC)134 and a digital-to-analog converters (DAC) 136. In this example, theDAC 136 generates the in-phase (I) and quadrature-phase (Q) signals 140that are applied to a modulator (not shown) in the transmitter 150. TheADC 134 and the DAC 136 also communicate with microprocessor 120, memory122, analog circuitry 124 and DSP 126 via bus 128. The DAC 136 convertsthe digital communication information within baseband subsystem 110 intoan analog signal for transmission by the transmitter 150. The connection140, while shown as two directed arrows, includes the information thatis to be transmitted by the transmitter 150 after conversion from thedigital domain to the analog domain.

The transmitter 150 includes a modulator (not shown), which modulatesthe analog information on connection 140 and provides a modulated signalto an upconverter (not shown). The transmitter 150 transforms themodulated signal on to an appropriate transmit frequency and providesthe upconverted signal to a power amplifier 180 via connection 184. Thepower amplifier 180 amplifies the signal to an appropriate power levelfor the system in which the portable transceiver 100 is designed tooperate.

Details of the transmitter 150 have been omitted, as they will beunderstood by those skilled in the art. For example, the data onconnection 140 is generally formatted by the baseband subsystem 110 intoin-phase (I) and quadrature (Q) components. The I and Q components maytake different forms and be formatted differently depending upon thecommunication standard being employed. For example, when the poweramplifier module is used in a constant-amplitude, phase (or frequency)modulation application such as the global system for mobilecommunications (GSM), the phase modulated information is provided by amodulator within the transmitter 150. When the power amplifier module isused in an application requiring both phase and amplitude modulationsuch as, for example, extended data rates for GSM evolution, referred toas EDGE, the Cartesian in-phase (I) and quadrature (Q) componentscontain both amplitude and phase information.

The power amplifier 180 supplies the amplified signal via connection 156to a front end module 162. The front end module comprises an antennasystem interface that may include, for example, a diplexer having afilter pair that allows simultaneous passage of both transmit signalsand receive signals, as known to those having ordinary skill in the art.The transmit signal is supplied from the front end module 162 to theantenna 160.

The power amplifier control element 185 determines the appropriate powerlevel at which the power amplifier 180 operates to amplify the transmitsignal.

A signal received by an antenna 160 is directed from the front endmodule 162 to the receiver 170. The receiver 170 includes variouscomponents to downconvert, filter, demodulate and recover a data signalfrom a received signal, as known to those skilled in the art. Ifimplemented using a direct conversion receiver (DCR), the receiver 170converts the received signal from an RF level to a baseband level (DC),or a near-baseband level (˜100 kHz). Alternatively, the received RFsignal may be downconverted to an intermediate frequency (IF) signal,depending on the system architecture. The recovered transmittedinformation is supplied via connection 186 to the ADC 134. The ADC 134converts these analog signals to a digital signal at baseband frequencyand transfers the signal via bus 128 to DSP 126 for further processing.

In an embodiment in accordance with the invention, the receiver 170includes a receive level (RXLEV) detect element 135. The RXLEV element135 develops a signal representative of the power level of the signalreceived from a base station with which the portable communicationdevice is operating. The RXLEV signal can be used to determine whetherthe portable communication device 100 is in a disadvantaged positionwith respect to the base station. Based on the level of the RXLEVsignal, the PCL software 155 can determine whether the power amplifiershould transmit maximum power during a RACH transmission, or whether thepower amplifier should transmit slightly less than maximum power toconserve power or transmit slightly more than maximum power to ensurereliable call establishment, as will be described below. While each RACHtransmission occurs at a maximum nominal power (power level 5 for aclass 4 mobile station, as mentioned above), the power of the RACHtransmission can be slightly modulated, as will be described below. Theslight change in the output power cannot violate the GSM recommendedmask requirement.

In an embodiment, the RXLEV signal is made available to the basebandsubsystem 110 so that a power control signal can be developed in thebaseband subsystem 110 and sent to the power amplifier control element185. The power control signal is referred to as MAXDAC because itrepresents a maximum digital-to-analog converter value that correspondsto the maximum power that can be transmitted by the power amplifier 180.

In an alternative embodiment, the RXLEV signal remains on the RF chipand is made available directly to the power amplifier control element185.

FIG. 2 is a schematic diagram illustrating a communication environment200 in which the system and method for dynamically improving callconnection operates. The communication environment 200 includes a basestation 202, which is in bi-directional radio frequency (RF)communication with a plurality of portable communication devices 214,216 and 218. The portable communication devices 214, 216 and 218 aresimilar to the portable communication device 100 described in FIG. 1.Typically, the base station will be in RF communication with manyportable communication devices. However, three portable communicationdevices are shown in FIG. 2 for simplicity of illustration. The portablecommunication devices 214, 216 and 218 are illustrated as beingdifferent distances from the base station 200. A first distance isillustrated using the reference numeral 204, a second distance isillustrated using the reference numeral 206, and a third distance isillustrated using the reference numeral 208.

In an exemplary embodiment, if a portable communication device, such asthe portable communication device 214, is physically close to the basestation 202, and preferably at or within the distance 204, then theamount of power transmitted by the portable communication device 214 tothe base station 202 can be relatively lower than, for example, theamount of power transmitted by a portable communication device that isfarther away from the base station 202 than the portable communicationdevice 214.

In this example, the portable communication device 216 is farther fromthe base station 202 than is the portable communication device 214.Similarly, the portable communication device 218 is farther away fromthe base station 202 than is the portable communication device 216. Inan example embodiment of the system and method for dynamically improvingcall connection, while each portable communication device 214, 216 and218 will send a maximum power RACH signal when it wishes to communicatewith the base station 202, there may be situations in which a slightlyhigher power RACH signal, or a slightly lower power RACH signal iswarranted. For example, because the portable communication device 218 isrelatively far from the base station 202, it may be desirable to causethe portable communication device 218 to send a RACH signal at aslightly higher power. Similarly, because the portable communicationdevice 214 is relatively close to the base station 202, it may bedesirable to cause the portable communication device 214 to send a RACHsignal at a slightly lower power.

The receiver (not shown, but refer to FIG. 1) within each portablecommunication device includes a receive level detect element 135. Theportable communication device 216 will be referred to here forsimplicity. The receive level detect element 135 provides a receivelevel reference signal, referred to as RXLEV, that is indicative of thesignal strength of the signal received from the base station 202 by theportable communication device 216. The strength of the signal receivedfrom the base station 202 is indicative of the condition of the radiofrequency (RF) communication environment between the base station 202and the portable communication device 216, and is therefore useful as anindicator of the amount of transmit power that should be expended by theportable communication device 216 to ensure a reliable two-way RFconnection to the base station 202. Because the portable communicationdevice 216 is located a nominal distance from the base station 202, amaximum power RACH signal is likely to yield acceptable results. In thisexample, a max power RACH signal is said to be transmitted with anominal power output, which is power level 5 for a class 4 mobilestation, from the power amplifier 180.

However, in a case such as that illustrated by the location of theportable communication device 214 relative to the base station 202, areceive level detect element 135 located in the portable communicationdevice 214 would likely indicate a very strong receive signal due to thesmall physical distance between the base station 202 and the portablecommunication device 214. In such an instance, the portablecommunication device 214 can transmit a max power RACH signal usingslightly less power and still likely achieve satisfactory communicationwith the base station 202, as will be described below.

In a case such as that illustrated by the location of the portablecommunication device 218, a receive level detect element 135 located inthe portable communication device 218 would likely indicate a relativelyweak receive signal due to the large distance between the base station202 and the portable communication device 218. In such an instance, theportable communication device 218 can transmit a max power RACH signalwith slightly more than maximum nominal power, which is power level 5for a class 4 mobile station, in order to achieve satisfactorycommunication with the base station 202.

It should be mentioned that physical distance between the base station202 and a portable communication device is used as an example toillustrate one factor that may influence the level of a signal receivedat a portable communication device and the general condition of atwo-way radio frequency communication channel between a base station anda mobile station. However, distance is not the only factor thatdetermines the level of a signal received at a portable communicationdevice. Many factors influence the strength of a signal received at aportable communication device. Factors include, for example, theterrain, the presence of obstacles, such as buildings, etc., the numberand location of other portable communication devices, etc. All suchfactors are contemplated herein.

In accordance with an embodiment of the system and method for improvingcall connection dynamically, the available receive level (RXLEV)information available in the portable communication device is used as ametric to determine whether the portable communication device is in adisadvantaged position with respect to the base station. If the portablecommunication device is in a disadvantaged position with respect to thebase station, then the transmit power level of the random access burstis boosted by an offset amount. For example, the offset amount can bedenoted as PWR_BOOST_OFFSET. The power control level software 155(FIG. 1) can measure the RXLEV against a threshold to determine whetherthe portable communication device is in a disadvantaged position and, ifthe portable communication device is indeed in a disadvantaged position,the power control level software 155 can boost the power level of therandom access (RACH) burst. In this manner, a higher likelihood ofestablishing a call connection on the first RACH signal is possible.

FIG. 3 is a graphical representation of the power output of the poweramplifier during a typical RACH burst 300. The curve 310 illustrates thedesired power output of the power amplifier 180 during a RACHtransmission. A transmit spectrum mask 302 defines the power and timeparameters within which the curve 310 must remain to comply withregulatory requirements. As shown in FIG. 3, the curve 310 indicatesthat output power remains below −70 dB until the beginning of the burst300. In this example, the portion of the burst in which the RACH requestis transmitted is 87 bits in duration, which corresponds to 321.2 μs,and is indicated using reference numeral 318. The ramp up of the curve310 occurs in the 18 μs preceding the beginning of the period 318 andthe ramp down of the curve 310 occurs in the 18 μs after the period 318.

The curve 320 indicates a desired power output of the power amplifier180 after being boosted by the power offset described above. Inaccordance with an embodiment of the system and method for dynamicallyimproving call connection, the power output of the power amplifier 180is boosted during a RACH burst if the level of the signal received fromthe base station 202, indicated using RXLEV, is below a predeterminedthreshold. Alternatively, the power output of the power amplifier 180can be reduced during a RACH burst if the level of the signal receivedfrom the base station 202, indicated using RXLEV, is above apredetermined threshold. In an embodiment, a max power RACH burst can bemodulated in the approximate range up to +1 to −1 dB and still remainwithin the mask 302.

RXLEV is the indication of the signal strength and is calculated asfollows. RXLEV=Measured Signal level+110. The portable communicationdevice is considered to be in a disadvantaged location when the measuredsignal level at the mobile station antenna is at or below −90 dBm. Thistranslates to a value of RXLEV between 0 and 20.

In an exemplary embodiment, the relationship between RXLEV and thesignal level is given in Table 1.

TABLE 1 RXLEV Signal Level  0 −110 dBm   1 −109 dBm   2 −108 dBm   3−107 dBm   4 −106 dBm   5 −105 dBm   6 −104 dBm   7 −103 dBm   8 −102dBm   9 −101 dBm  10 −100 dBm  11 −99 dBm 12 −98 dBm 13 −97 dBm 14 −96dBm 15 −95 dBm 16 −94 dBm 17 −93 dBm 18 −92 dBm 19 −91 dBm 20 −90 dBm 21−89 dBm . . . 40 −70 dBm

When the level of the RXLEV signal indicates that the portablecommunication device is in a disadvantaged location, the transmit poweris raised by an amount equal to PWR_BOOST_OFFSET.

In an embodiment, the power control level software 155 (FIG. 1) can beimplemented using two registers. A register 156 (FIG. 1) can contain avalue for the receive level threshold, RXLEV_THRESHOLD, which in thisexample is 20 (corresponding to −90 dBm), but can be any value dependingon implementation. A second register 157 (FIG. 1) can contain a valuefor the value PWR_BOOST_OFFSET, which can be in the same format as thesignal MAXDAC. If the value of RXLEV measured in the receiver 170(FIG. 1) is less than RXLEV_THRESHOLD, then the value ofPWR_BOOST_OFFSET is added to the MAXDAC value that will be used togenerate the maximum power for the RACH burst. However, if the level ofRXLEV is greater than or equal to the threshold RXLEV_THRESHOLD, nopower boost is added to the value of MAXDAC that will be used for theRACH burst. A third register 158 can contain the information related tothe low threshold, RXLEV_THRESHOLD_LOW, and the high threshold,RXLEV_THRESHOLD_HIGH, to be described below.

In an embodiment, the default value of the RXLEV_THRESHOLD can be 20,but can be changed at power on reset (POR) programming. In anembodiment, the default value of PWR_BOOST_OFFSET=DAC setting count for0.5 dB. For example, when the portable communication device iscalibrated, power amplifier output power is equated to DAC value. In anembodiment, the PWR_BOOST_OFFSET value corresponds to approximately 0.5dB, which corresponds to the DAC count that would be equated with 0.5 dBfor the particular power amplifier. The value of PWR_BOOST_OFFSET can bechanged at power on reset programming. To disable the additional powerboost, the value of PWR_BOOST_OFFSET should be programmed to 0 and/orRXLEV_THRESHOLD should be programmed a negative integer value. Todisable the power decrease, the value of PWR_DECREASE_OFFSET should beprogrammed to 0 and/or RXLEV_THRESHOLD should be programmed a negativeinteger value. Both RXLEV_THRESHOLD, PWR_BOOST_OFFSET andPWR_DECREASE_OFFSET can be adjusted and programmed for best performance.

FIG. 4 is a graphical representation of a portion of the output burst ofFIG. 3, illustrating the operation of the system and method fordynamically improving call connection.

A portion of the spectrum mask 302 is shown for reference. The 0 dB linerepresents a nominal maximum power output of the power amplifier duringthe RACH burst. The actual power output is determined when the poweramplifier is calibrated. Therefore, the curve 310 will coincide with the0 dB line, regardless of the actual power output. The curve 310represents the max power output of the power amplifier during a nominalmax power RACH burst, and can be located anywhere within the mask 302,i.e., at a power of 33 dBm, +/−1 dB, for a class 4 mobile station. Thecurve 310 represents the output of the power amplifier under a normal,non-power boosted RACH burst. The curve 320 illustrates the actual poweroutput of the power amplifier 180 when the value, PWR_BOOST_OFFSET 322is added to the output power. The curve 325 illustrates the actual poweroutput of the power amplifier 180 when the value, PWR_DECREASE_OFFSET327 is subtracted from the output power. The output power of the poweramplifier 180 can be increased or decreased by a small value between −1dB and +1 dB, depending on factors such as the actual maximum power thatthe power amplifier is able to transmit, the amount of power availablein the power amplifier (i.e., power amplifier headroom), and otherfactors. For example, the output power of the power amplifier 180 isincreased by the value corresponding to PWR_RBOOST_OFFSET when the valueof the RXLEV signal is below the threshold RXLEV_THRESHOLD, indicatingthat the portable communication device is in a weak signal receptionarea with respect to the base station 202. In an embodiment, the powercan be nominally increased by approximately 0.5 dB. However, the boostedpower output still remains within the mask 302. Similarly, the outputpower of the power amplifier 180 is decreased by the value correspondingto PWR_DECREASE_OFFSET when the value of the RXLEV signal is above thethreshold RXLEV_THRESHOLD, indicating that the portable communicationdevice is in a strong signal reception area with respect to the basestation 202. In an embodiment, the power can be nominally decreased byapproximately 0.5 dB. However, the reduced power output still remainswithin the mask 302.

In an embodiment, the baseband subsystem 110 computes the setting of themaximum DAC (MAXDAC) value for the power control level and also programsthe settings to the RF/MSD subsystem 130. The RFIC uses the MAXDAC togenerate the power profile for the actual transmit burst. However, in analternative embodiment, the computation of the value MAXDAC for thepower control level and the generation of the power profile are done inthe RF/MSD subsystem 130. In such an embodiment, the baseband subsystem110 may program the power control level, but the RF/MSD subsystem 130provides the MAXDAC value directly from the receive level detect element135 to the power amplifier control element 185.

FIG. 5 is a flow chart illustrating the operation of an embodiment ofthe method for dynamically improving call connection. The blocks in theflowchart can be performed in the order shown, out of the order shown,or can be performed in parallel. In block 402, the level of the signalreceived from a base station 202 is measured by the receive level detectelement 135. The receive level detect element 135 then generates theRXLEV signal.

In block 404, the value of the RXLEV signal is compared against areceive level threshold signal, RXLEV_THRESHOLD. If, it is determined inblock 404 that the value of the receive level signal RXLEV is greaterthan the threshold, a nominal (maximum) power RACH burst is initiated inblock 406 and the process ends.

If however, in block 404 it is determined that the value of the receivelevel signal RXLEV is less than the threshold, then, in block 408, theoutput power of the power amplifier 180 is increased by an amountbetween −1 dB and +1 dB (referred to as PWR_BOOST_OFFSET) and anincreased power RACH burst is transmitted. In an embodiment, the powercan be increased by approximately 0.5 dB. The increased-power RACH bursthas a higher likelihood of being received at the base station than anormal RACH transmission, thereby improving the chance of callestablishment using a single RACH burst. The process then ends.

FIG. 6 is a flow chart illustrating the operation of an alternativeembodiment of the method for dynamically improving call connection. Theblocks in the flowchart can be performed in the order shown, out of theorder shown, or can be performed in parallel. In block 502, the level ofthe signal received from a base station 202 is measured by the receivelevel detect element 135. The receive level detect element 135 thengenerates the RXLEV signal.

In block 504, the value of the RXLEV signal is compared against areceive level threshold signal, RXLEV_THRESHOLD. If, it is determined inblock 504 that the value of the receive level signal RXLEV is less thanthe threshold, a nominal (maximum) power RACH burst is initiated inblock 506 and the process ends.

If however, in block 504 it is determined that the value of the receivelevel signal RXLEV is greater than the threshold, then, in block 508,the output power of the power amplifier 180 is decreased by an amountbetween −1 dB and +1 dB (referred to as PWR_DECREASE_OFFSET) and andecreased power RACH burst is transmitted. In an embodiment, the powercan be decreased by approximately 0.5 dB. The decreased-power RACH burstreduces power consumption in a situation in which a reduced power RACHburst is likely to be adequately received at the base station. Theprocess then ends.

FIG. 7 is a flow chart illustrating the operation of another alternativeembodiment of the method for dynamically improving call connection. Theblocks in the flowchart can be performed in the order shown, out of theorder shown, or can be performed in parallel. In block 602, the level ofthe signal received from a base station 202 is measured by the receivelevel detect element 135. The receive level detect element 135 thengenerates the RXLEV signal.

In block 604, the value of the RXLEV signal is compared against areceive level threshold signal, RXLEV_THRESHOLD_LOW. If, in block 604 itis determined that the value of the receive level signal RXLEV is lessthan the low threshold, then, in block 606, the output power of thepower amplifier 180 is increased by the amount associated with thesignal, PWR_BOOST_OFFSET, and an increased power RACH burst istransmitted, as described above. The increased-power RACH burst has ahigher likelihood of being received at the base station, therebyimproving the chance of call establishment using a single RACH burst.The process then ends.

If, however, it is determined in block 604 that the value of the receivelevel signal RXLEV is greater than the low threshold, then, in block612, it is determined whether the value of the receive signal levelRXLEV is greater than a high threshold, RXLEV_THRESHOLD_HIGH. If, inblock 612 it is determined that the value of the receive signal RXLEV ishigher than the value of the high threshold, then, in block 614 thetransmit power is reduced by the amount associated with the signal,PWR_DECREASE_OFFSET, within the range of −1 dB and +1 dB, but stillremaining within the mask 302 (FIG. 4) and a reduced power RACH burst istransmitted. In an embodiment, the power can be reduced by approximately0.5 dB. The process then ends.

If, in block 612 it is determined that the value of the receive signalRXLEV is lower than the value of the high threshold, then, in block 616a normal RACH burst is transmitted. The process then ends. In thismanner, a window is created between the low threshold,RXLEV_THRESHOLD_LOW, and the high threshold, RXLEV_THRESHOLD_HIGH, thusallowing a three-case decision process to send a reduced power RACHburst, a normal power RACH burst, or an increased power RACH burst,depending on the value of the receive signal as indicated by the signalRXLEV. For example, for a receive signal between −90 dBm (RXLEV=20) and−70 dBm (RXLEV=40), as a threshold window, a nominal max power RACHburst is transmitted. For a receive signal higher than −70 dBm(RXLEV>40), the RACH power is adjusted lower by the offset valuePWR_DECREASE_OFFSET; and for a receive signal lower than −90 dBm(RXLEV<20), the RACH power is adjusted higher by the offset valuePWR_BOOST_OFFSET.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof this invention. Accordingly, the invention is not to be restrictedexcept in light of the attached claims and their equivalents.

1. A method for increasing an output of a power amplifier of a portablecommunication device, comprising: determining a power level of a signalreceived at the portable communication device; generating a receivereference signal (RXLEV) that is indicative of the power level of thesignal received at the portable communication device; determiningwhether the receive reference signal is below a threshold value; andwhen the receive reference signal is below the threshold value,increasing a power output of a power amplifier in the portablecommunication device during a random access channel signal transmission.